Process of and apparatus for obtaining oxids of nitrogen from atmospheric air.



F. I. DU PONT.

PROCESS 0F VAND APARMUS FOR OBTAINING OXIDS 0F NHRUGEN FRDM ATMOSPHERIC AIR.

FPUCATION flLED MFLZO, |915. 1,31 1,594. Patented July 29, 1919.

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INVENTOR l "Il .I,..F

F. I. DU PONT.

PROCESS 0F AND APPARATUS FUR OBTAINING OXIDS 0F NIIROGEN FROM ATMOSPHERIC AIR.

APPLICATION FILED MAR. 26. 1915. 1,31 1,594. Damned Ju1y29, 1919.

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Il l Igneethod of heating, other t UNITED STATES PATENT OFFICE..

.FRANCIS I. nu roN'r, or WILMINGTON, DELAWARE, AssIeNon. To DELAWARE CHEMICAL ENGINEmING COMPANY, or WrmrNe'roN, DELAWAnE. A Cos.F

PORATION F DELAWARE.

PROCESSQF .AN'D4 APPARATUS FOB OBTAIN'ING GXIDS 0F NITBOGEN B'ROII ATMOS- PB'EBIC. AIB.

Specification of Letters Patent.

Patented July 29, 1919.

Application led Burch 26, 1,915. Serial N 0. 17,116.

To all whom z'tmay concern Be it known that I, FRANCIS I. DU PONT, a citizen of the United States, residin at Wilmington, county of New Castle and tate of Delaware, have invented a new and use ful Improvement in Processes of and Apparatus for Obtaining Oxids of Nitro n from Atmospheric Alr, of which the ollowing is a full, clear,- and exact description, reference `bein lad to the accompanying drawings,`whic form a part of this specifica*ticle-3 y w It is well understood that when a mixture1 of oxygen and nitrogen is raised to a certain high temperature, a combination takes place and oxids of nitrogen are formed. Usually, the heating is accomplished by'means of an electric arc because, by this means, an intense heat is obtainable without depending upon thewalls of the chamber inwhich the' heating is accomplished. In other. words, the electric arc produces an intense heat and will, itself, keep the heat away from the walls of the chamber provided the electrodes are sufficiently far away. As the temperature required isgreater than any material, except carbon, will stand, and as carbon cani not be'used on a'ccount of its aliinity for oxyit is generally reco ized that no an. the electric` arc is practicable.

fn the utilization of the electric arcl many inventors have proceeded on the theory that byx forcing a maximum amount of atmosp e ric air through the arc, or by diii'using the arc throughout a great volume of space,

the best results will be secured. An appreciation of the nature y of an electric arc and' of the conditions most favorable to its formation will make it evident that the results sought are impossible of accomplishment and that the formation reaction that occurs proceeds in spite of, and not because of, the special but mistaken means employed to promote it. f l

An arc appearsto the eye as a streak of light `between two electrodes. Up to a oertain point, gases are. a better conductor of electricity in proportion as they reach a ,state of great rarity. Maximum conduc- `tivty, therefore, 1s at a point 'where there in the space through which` is very little the'cumnt igsas traveling. iFrom' this 'it is apparent that the electric arc consists in air heated to such anv extent that it is greatly rarefied. Therefore the condition automatically exists that actually within any given arc there is ver little air.

yIt will `there ore, be appreciated that it is impossible to pass enough air through an J arc to produce oxlds of nltrogen 1n commercial quantities. It will also *be appreciatedthat the attempt, by diffusion of the arc, to force the same through a relatively large imity to, but out of the path of, an arc of' high current density. The execution of this process involves the employment of. a relatively long and narrow chamber 'or tube. Further objects of the invention al'e: to avoid disturbing the natural axial position of the arc in t e tube, to render the tube wall non-conductive even with an arc of high current density, to prevent burning out of either electrode, to avoid the danger of displacing, disrupting or short circuiting the arc, and, in general, to provide an apparatus operating on a principle which takes the utmost advantage of the physical characteristics of an electric arc hereinbefore discussed.

A preferredA construction of apparatus embodying my invention and adapted to carry out the process embodying my invention is shown in the drawings, in which- Figure 1 is a longitudinal view, principally in section, 'of the entire a aratus.

ig. 2 is a. cross section through t e center of the apparatus. Fig. 3 is a detail sectional view of the air discharge end of one of the electrodes. Fig. 4 is a diagrammatic per- Spective view showing direction of the air currents in the reaction tube. A cylinder a composed of two parts connected at the center as herelnater described,

has ends c through which and the cylinder extends a tube b, which is also Composed of two parts con ted at the center as hereinafter described. The tube b projects beyond the cylinder at sich end. surmundmg wh end of tube b is packing confined, by a ring d, against a. boss e on which the ring is threaded.

Into each end of tube b extends an electrode f. Each electrode is slidable in a head g, which abuts' against the end of tube b. Packing surrounds each tube b and is held between the head g and a ring h surrounding the tube and threaded on the head. A stufling box z' is applied to each electrode and the corresponding head.

By the described construction the cylinder a is rendered water tight and the tube b gas ti ht.

grIhe outer end of each electrode is carried by a holder ic. The two holders are connected to opposite poles of a source of electric current supply. Each holder la (which is of electrically conductive material) is supported on legs l (of non-conductive vmaterial) extending upward from a slide m slidable longitudinally, or in the direction of extension of the cylinder a, tube b and electrodes f, in `Ways on a. base n.

The two slides are operable in unison in opposite directions. To so operate them I have shown each slide provided with a longitudinally extending rack o. Between and engaging both racks is a pinion p.

It is obvious that by turning pinion p the two electrodes may be moved toward each other and into contact to close the circuit and then caused to recede from each other to establish the arc.

Each electrode is a hollow rod having an enlarged end in front of which is carried a block of carbon q, constituting a pole or the electrode proper. Each holder k is connected by means of arubber hose 1' with a compressed air supply pipe s; the holder being hollow to permit of the passage of air therethrough to the electrode.

The end wall of each electrode is provided with perforations f which extend at an oblique angle to a plane at a right angle to the axis of the tube, thereb causi the air to enter the tube with a spiral motion, producing a vortex through the central cavity of which the arc is adapted to pass.

It has hereinbefore been stated that the tube b is made in two halves. The inner ends of the tubes are flared outward to form a central chamber b'. The inner flared ends of the tubes have opposing annular flanges between which is confined the neck of a ring t. Rings u, within the cylinder a, confine the flanges of the tube b against the neck of the ring t. Packing rings are confined between said flanges and the ring neck and between said flanges and the rings u. The body of the ring t has an annular passage t2 which communicates, by passages t extendin, tlnough the neck of the ring, with the central chamber b'. The assag t' extendV in a plane at right ang es to the axis of the tube but at oblique angles to intersecting radii, their direction of extension being such as not to affect the vortex motion of theoutflow of air from chamber b' and not to cause any air currents which might blow the arc to one side.

The ring t connects with an outflow pipe 'v which carries off the combined gases to the concentrating plant.

The cylinder a communicates at one end with a water inflow pipe rw and at the other end with a water discharge pipe as. A pipe y connects the two ends of the cylinder.

The cylinder a is of glass and the tube b is of silica. Y

In operation the electrodes are brought together to close the circuit and are then moved outward in opposite directions, establishing an arc. Water is admitted to the cylinder so that the tube b is water cooled. The application of a cooling medium to the tube is of importance, as otherwise the tube, although of non-conducting material, would become conductive at the high temperature which my process contemplates, resulting in short-circuiting of the arc.

When air is admitted t'hrough pipes r it passes frolneach end of the tube to the center thereof in the paths indicated in the diagram, Fig. 4. It is important that the whirling motion of the air in both ends of the tube should be in the same direction around the axis of the tube, so that when the gases reach the central chamber there will be no conflicting currents.

The arrangement is such that the main body of the air traversing the tube does not pass through the arc but around it and in close proximity thereto.

The purpose and function of the air current in my process is not to use Vit as a means to maintain the are stable. On the contrary the problem is to maintain the arc in the axial position which the arc would normally occupy if there were no current of air passing through the tube and at the same time bring the maximum amount of air in close proximity to the arc.

The problem is solved by the described method of admitting the air, with the resultant whirling motion described, within a cooled insulating tube of relatively small diameter. The action may be explained as follows:

Owing to the action of centrifugal force whereby the coolest and heaviest air tends away from the center of the tube and the hottest Yand therefore lightest air tends to remain in the center of the tube, it is manifest that the normal axial position of the arc. that is to say, the position which the are would normally occupy if there were no current of air passing through the tube, is not disturbed by the current of air.

Owing to the cooled insulating tube, the

axial position ofthe arc and the centrifugal l action of the whirlin mass of air, a greater amount of air can brought into close proximity to an arc than is possible any other way. By maintaining the Wall of the reaction tube non-conducting, they may be brought in close proximity to the are without danger of short circuiting.

-The enlarged central chamber, together with the oblique exit passages arranged around its periphery, are also of importance, in that thereby the suction produced by the outgoing gases operates equally in all directions and thereforedoes not tend to dis place the arc.

It is also necessary to uard against the overheatingV of one or bot electrodes. Ex-

perience shows that where the gases travel the latter.

from one electrode to the other, soon burns out. The provision, inmy invention, whereby the air travels from both `electrodes toward an intermediate outlet, in-

stead of from one electrode to the other,

avoids overheating either electrode.

In this specification the word air has been used. r I wish to say that this'is 'intended to include all mixtures of oxygen tion, what I claim and desire to and nitrogen, ,including those in which the air is enriched in oxygen.

Having now fully described my invenprotect by Letters Patent is:

Y i 1. The process of formingloxids of nitro` gen from mixtures of oxygen and nitrogen which consists in formingan electric arc, passing the gases to be acted upon in two streams flowing along the arc toward each other, causing the gases at the junctpre of theAk two streams to escape outwardly, maintaining. the walls of the reaction chamber non-conducting upto the point of escape for the gases, and cooling the gases during their outward flow away from the arc at the junction of the two streams.

2. An apparatus of the character described comprising -twol aliningv tubular .members having'gas inlets, an intermediate V connecting chamber of substantially greater- Aim.

diameter than the tubular members and provided with means for the escape of gases,

and chambers for a cooling medium on .op,

posite sidesof the intermediate chamber and surrounding therespective tubular members and adapted to maintain said coolin'g medium in contact with the tubes as far as the inner opposite extremities of the same and with the side walls of the' intermediate chamber. 3. An apparatus of the character described comprisin a tubeti poles within the tube between'whi anelectric arc is formed, gas inlet ports arranged to create a` vortex -v within the tube, and gas outlet ports arranged obliquely to intersecting radii of the tube.

scribedcomprising a tube,

4i.. An apparatus of the character described comprising a tube forming a reaction chamber, poles between which an electric arc is formed, gas inlet ports in the L scribed comprising a tube, lhollow electrodes projectiiiginto opposite ends of the' tube,

poles carried by said electrodes, and gas ports in the front end walls of both electrodes.

the character dehollow electrodes projecting into opposite ends of the tube, poles carried by said electrodes, gas inlet ports 'in the.` front end wall of both electrodes, and gas outlet ports communicating with an intermediate part of the tube.

7. An apparatus of the character described comprising alining tubular portions having as inlets and an enlarged central portion geving means allowing the escape of ases, two cooling chambers inclosing the tubular portions of the reaction chamber, and means allowin the circulation of a cooling Huid between 51e two cylindrical chainbers.

8. An apparatus of the character de- 6; An apparatus of` `scribed comprising a tube forming a reaction chamber, a hollow lelectrode projecting into said tube, a pole carried by said electrode, and gas inlet ports in the front end wall of the electrode, .the axis ofsaid ports arranged obliquely to planes at right angles to the axis of the tube.

9. A n apparatus of the" character de scribed comprising two alining tubular members having gas inlets and provided with enlarged opposing ends, poles in proximity to theg'as inlets, a ringconned between the peripheries of said opposing ends, andA gas outlet ports in said ring.

10.V An apparatus of the .character de scribed comprising two alining tubular members having gas inlets and provided with enlarged opposing to the gas-outlets, and a hollow ring hav ing aportd neck conned between the peripheries of said opposing ends.

11. Ai lapparatus of the character described comprising two alining tubular members having j gas inlets and provided with enlarged opposing ends, poles in proximity to the gas inlets, 'two cylindrical water- `cliambers surrounding the lrespective tubular members, a ring separating said chamends, poles in proximity scribed comprising a reaction chamber, gas inlets at opposite ends thereof, a rin surrounding the central portion thereo and provided with ports aifording gas outlets from the reaction chamber two cylindrical water chambers separated by said rlng and surrounding the two halves of the reaction chamber, a water discharge pipe communieating with vone water chamber, a. Water admission pipe communicating with the other water chamber, and a pipe connecting the two water chambers.

13. An apparatus of the character described comprising a relatively long and narrow reaction chamber having gas exlts opening from the central portion thereof, hollow axially movable electrodes entering opposite ends of the reaction chamber, Said electrodes having enlarged ends provided with ports for admission of gases to the reaction chamber and pole pieces carried by and projecting in front of said electrode ends.

14. An apparatus of the character described comprising a relatively long and narrow reaction chamber having gas exits opening from the central portion thereof, hollow axially movable electrodes entering opposite ends of the reaction chamber, poles carried by the electrodes, said electrodes being ported to allow gases to pass from their interior to the reaction chamber, and means to move said electrodes toward and from each other.

15. An apparatus of the character described comprising a relatively long and narrow reaction chamber having gas exits opening from the central portion thereof, hollow axially movable electrodes entering opposite ends of the reaction chamber, poles carried by the electrodes, said electrodes being ported to allow gases to pass from their interior to the reaction chamber, .hollow holders carrying said electrodes, air inlets communicating with the holders, and

means to move the holders toward and from each other.

16. An apparatus of the character described comprising a relatively long and narrow reaction chamber having gas exits opening from the central portion thereof, hollow electrodes entering opposite ends of the reaction chamber, poles carried by the electrodes, said electrodes being ported to allow gases to pass from their interior to the reaction chamber, hollow holders carrying said electrodes, air inlets communicatin with the holders, slides one for each ho der, means to support and insulate each holder from its slide, and means to operate said slides in unison.

17. An apparatus of the character descri comprising a relatively long and narrow reaction chamber having gas exits opening from the central portion thereof, hollow axially movable electrodes entering opposite ends of the reaction chamber, poles carried by the electrodes, said electrodes being ported to allow gases to ass from their interior to the reaction cham r, means to slide said electrodes toward and from each other, and heads applied to opposite ends of vthe tube and through which the electrodes respectively slide.

18. An apparatus of the character described comprising two alining tubes, poles in the respective tubes between which an electric arc is formed, gas inlet ports in the respective tubes, and a chamber, between and communicating with the tubes, provided with means allowing the escape of gases and of a diameter substantially greater than that of the tube.

In testimony of which invention I have hereunto set my hand at Wilmington, Del., on this 22nd day of March, 1915.

FRANCIS I. DU PONT.

Witnesses:

EMILY M. ANDERSON, AARON FINGER. 

